In the past, when the printed circuit board was first developed, it was hailed as a major advance in electronics technology over hard wired boards in that it permitted more components to be mounted in smaller areas. As the printed circuit board technology evolved, many complex chemical processing techniques developed for improving the number and configuration of circuit lines which could be placed on a circuit board.
Since "printed" circuit board technology involves photographic processes, many different chemical baths are required which means expenses in processing
and for the processing equipment. Over 55 different steps are required to make a single printed circuit board. In addition, the need for different chemical steps has resulted in serious problems with chemical waste control both in the vapors and residues of the various processes.
Heretofore, almost all developments in printed circuit board technology have been directed towards improved chemical processes and improved printing techniques. These refinements of technology are rapidly reaching the point of minimal return.
Further, there have been major problems with making connections from the circuit lines on one side of the circuit board to the other and of making adequate connections of components to the boards. This has resulted in a search for a method of making improved conductive connections via the through-holes provided in the board for component mounting.
Originally, the distances between circuit lines were relatively wide and in 1965 the state of the art was approximately 12 mils. By 1980 they were down to 6 mils and current projections are that the maximum theoretical limit using known printed circuit technology is about 2 mils with 0.25 mil thick copper laminations.
Closer line placements are required and this requirement has increased the demand for better insulation between lines as well as better immunity to airborne and chemical processing contaminants. Not only has the progress of printed circuit technology consistantly challenged the plating industry for innovations, but also for economy in the face of rising raw material and energy prices. Further, a greater sense of awareness of environmental protection requirements and for health and safety in the work place have posed tremendous challenges for the industry.
With the new requirements posed and the the new problems, there has been a long felt need for major innovation with respect to processes and equipment in circuit board technology.